1. Field of the Invention
The present invention relates to optical disk and magneto-optical disk recording and playback devices which are used with computers and image processing devices.
2. Description of the Related Art
Generally, optical disks and magneto-optical disks (collectively referred to as "optical disks") are composed of concentric shaped or spiral shaped tracks on a recording surface. If one track circumference is counted as a disk, then several thousand tracks can be configured on an optical disk.
The tracks of an optical disk are divided into multiple regions called sectors. Within these sectors are data parts for the purpose of recording an identification (ID) part, in which the sector address, etc. is recorded, and the user data.
When a recording and playback device records data on an optical disk, the data that is received from a host computer, etc. is stored all at once in a buffer memory. Then, the typical recording method reads the data from the buffer memory and executes recording processing in relation to the disk. When the amount of data to be recorded exceeds the recording capacity of the buffer memory, recording processing is executed by taking the number of sectors equivalent to the recording capacity of the buffer memory to be the recording unit for one pass, and recording processing is executed repeatedly.
Moreover, it should be noted that optical disks have a higher medium bit error rate compared to magnetic disks. For this reason, during the process of recording onto an optical disk with an optical disk recording and playback device, after writing data onto the optical disk, verification processing is executed in order to confirm whether or not the data that has been written can be read back normally. This processing is called the RAW (Read After Write) check. In addition, during the process of recording onto a rewritable optical magnetic disk, generally, an erasure operation (initialization) is executed prior to writing. Such an erasure operation is carried out for the purpose of erasing data that is already recorded in the region where writing is to be executed on the optical disk.
Over the last several years there has been a remarkable increase in the capacity of external memory devices for computers and the like. Optical disk recording and playback devices are no exception to such increases in capacity. Accordingly, there have been several methods proposed to increase the recording capacity of optical disks.
One optical disk recording method that has been used for a long time is the CAV (constant angular velocity) method. In the CAV method, an optical disk is rotated at a fixed number of rotations and the recording and playback frequency is made to be the same on any track of the optical disk. In the CAV method, the linear velocity becomes faster the further out the track. Because the recording frequency is the same on every track, the lengths of the recording marks become longer the further out toward the periphery of the optical disk. Consequently, recording density becomes smaller the further out to the periphery.
Another method, the MCAV (modified CAV) method is one that greatly increases the recording capacity compared to the CAV method. In MCAV systems, the optical disk is rotated at a fixed number of rotations, and the recording and playback frequency becomes higher toward the periphery. Thus, the recording density is roughly a fixed value on any track. That is, the length of the recording marks is nearly fixed for every track.
Also, one practical form of an MCAV system is called the Zone CAV method. The Zone CAV method divides disk tracks into multiple groups of multiple tracks. These groups are called zones. These multiple zones are in a donut shape. Tracks which belong to the same zone execute recording and playback at the same clock frequency. Thus, the recording and playback frequencies become higher the further out the zone (the zones which have faster linear velocities). In this way, the recording density of the zones can be made uniform.
The recording and playback of disks which have a zone CAV format are executed with the time per track (the time it takes the disk to make one rotation) being fixed. However, because the recording and playback frequency differs depending on the respective zones, the number of sectors per track varies depending on the zone. Thus, there is the characteristic that the number of sectors per track increases the higher the recording and playback frequency of the zone (the further the zone is toward the periphery). In the MCAV method as well, the number of sectors per track increases the more the track is to the periphery of the disk.
When considering the aforementioned kinds of operation of recording onto an optical disk that has MCAV or Zone CAV formatting, during the recording operation in the interval from the completion of initialization up to the beginning of data writing, or from the completion of data writing up to the beginning of verification, there is always an optical beam seek operation time generated (the time to determine the position for moving the head from the track at a position where data writing has been completed to the track at a next position where the data writing is to begin again), and a wait time after the seek operation has been completed until the specified sector within that track is reached (the sector at which data writing is to begin).
The seek operation time is time that is unavoidable in order for the device to operate, but the wait time is wasted time. Consequently, it is desirable to shorten the wait time.
As in the past, when executing the recording operation in multiple units of sectors corresponding to the recording capacity of the buffer, the wasted wait time increases and decreases depending on the zone. The reason for this is that the number of sectors per track varies depending on the zone. When there is little wait time, there is no problem, but as the wait time increases there is the problem of inviting a reduction in the data transfer rate.
The aforementioned problems are merely exemplary of the problems addressed and solved by the present invention.